
it's probably bc I've never been loved back by someone I love but I think if you know that the person you love loves you back, no matter what circumstances you are in, I would want to be with them and savour the feelings we have for each other while we still have the time do it before it's too late

I think that's a really nice but idealistic way of thinking, and definitely one everyone wishes they could have. But circumstances don't always allow us to do that. The author does a pretty good job laying out all the backstory for both of these characters, but doesn't explain all the psychology behind it for us (which I think is nice).
If you think about Min Gyeom's upbringing and all that he's been through, his actions now are pretty logical. He doesn't have the luxury of acting on just his emotions at this point. He's never really been loved by anyone before, including his own parents, so it makes perfect sense that he can't simply just choose love over a safe place to live. I doubt he can even believe that love is enough to get people through any obstacle. For him that'd be one hell of a leap of faith -- and trust is probably one of the most difficult things for him to grasp.
WHAT HAPPENED TO KOUCHAN AND HADES
... NOW THAT YOU ASKED .